Our objective is to continue our research in the application of stochastic models to problems in the epidemiology of infectious disease. Currently we are working on a simulation model for the study of immunization strateges, for both inactivated and live virus vaccines, in the control of pandemic strains of influenza A viruses. We will also include problems concerning the antigenic drift variants of the HongKong 1957 virus. The model is for a highly structured community population and allows for differential contact rates by age and for family mixing, playgroups of preschool children, gradeschools, highschools, neighborhood clusters of families and in the entire community. The model is highly flexible with respect to the properties which may be assigned to individuals, and also with respect to properties of the infectious agent. Individuals are assigned age class, mixing pattern, relative susceptibility, relative infectiousness to others. Properties of the agent are reflected in the lengths of the latent and infectivity periods which are taken as random variables. The occurrence of illness and withdrawal from mixing outside the home are random events with assignable parameters to reflect the pathogenicity of the agent. Response to vaccination is also treated as a random variable and the failure rate and patterns of developing immunity are assignable. Age and mixing group specific contact rate may be changed during the course of the epidemic to reflect such control actions as closing of the schools. The model has sufficient fexibility to make it appropriate for the study of many agens other than influenza. The project provides opportunity for training of students in the development and use of stochastic simulation models.